1. Field of Invention
This invention relates to a biomaterial and more specifically a high molecular weight, multifunctional acrylate cross-linking composition that, when formulated with other compounds will self-etch and self-adhere to hard tissues, such as enamel, dentin, and bone.
2. Description of the Related Art
The use of synthetic materials to expedite healing is becoming more widespread. A burgeoning area of growth is the use of relatively inert hardening agents for use as adhesives or as a substitute for hard tissue. Hard tissue typically means tissues that have become mineralized, or tissue having a firm intercellular substance, such as enamel, dentin, cartilage, and bone. Bone and tooth structure, such as enamel, dentin and cementum, have certain compositional and morphologic similarities. Like enamel and dentin, bone consists primarily of inorganic material, which is almost exclusively in the form of an apatite of calcium and phosphate that resembles hydroxylapatite, and a lesser amount of organic material, which is 90% collagen. Morphologic similarities also exist. Enamel and dentin both contain tubules which meet their respective surfaces at a perpendicular angle, while bone contains tube-like Haversian Canals. The Haversian Canals run parallel to the bone's surface, but Volkmann's Canals, which run from them meet the bone surface at a perpendicular angle.
Teeth that are fractured or have lost dental restorations often involve exposed dentin. These exposed teeth are prone to tooth decay, and patients usually experience pain. For treatment purposes, the exposed teeth are usually restored with permanent dental restorations. However, definitive dental restorations often are not performed in a timely fashion. In these cases, temporary dental restorations (fillings) are usually placed onto the exposed teeth. There are a variety of restorative dental materials that can be used as temporary fillings.
The materials most commonly chosen as temporary fillings are zinc oxide-eugenol (ZOE) compounds, glass-ionomer materials, and resin-based dental materials. These filling materials are retained in teeth through mechanical retention and/or chemical bonding with the tooth structure.
ZOE fillings require mechanical retention. These materials are relatively weak compared to the other types of temporary filling materials.
Glass-ionomer dental filling materials can bond to tooth structure without the need of a separately applied bonding agent. In addition, glass-ionomer materials release fluoride, which strengthens the surface of the tooth. A disadvantage of glass-ionomer dental filling materials is their relatively long setting time and concomitant sensitivity to moisture. Moisture exposure can result in premature disintegration of the glass-ionomer material and reduce bond strength. Furthermore, the chemical bond formed between glass-ionomers and tooth structure is relatively weak.
Resin-based filling materials can be bond to teeth using both mechanical and chemical retentions. Bonding of resin-based dental materials to tooth structure is currently achieved through a multi-step process. A dentin-enamel bonding agent must be applied to the tooth prior to placing the dental material. Applying this bonding agent often requires multiple steps and a significant amount of clinical time. Misapplication of the bonding material may also occur.
In general, retention of temporary fillings through chemical bonding is quicker, requires less preparation of the tooth, and is usually stronger. Often teeth can be temporarily restored with dental materials using only chemical bonding. Acid etching of the tooth surface are often performed to improve adhesion of resin-based filling materials by promoting mechanical retention. However, many acid-etching agents must be removed prior to application of the bonding agents, which further increases clinical time. Acid etching can also cause dental sensitivity in some patients.
There are dental restorative materials on the market that are self-etching adhesives. These compositions generally use water and/or organic solvents and take a liquid form. Consequently, these self-etching adhesives have a short shelf-life, which may pose additional problems for storage. For example, these materials may experience a premature setting in extreme conditions such as those presented in a desert battlefield. Furthermore, many of these formulations require multiple applications of a single component or application of several separate components. Therefore, they require more clinical time to apply than the inventive formulation.
U.S. Pub. No. 2007/0244215 A1 by Junjie Sang, describes a one-component self-etching dental adhesive, which requires a simple one-coat application, without the need of separate acid-etching, priming or bonding step. This is achieved through the employment of a hydrolytically stable, acidic, high-strength adhesive monomer (such as PENTA) with a stable, bifunctional, hydrophilic monomer (such as AHPMA) that yields greater cross-linking. However, this material lacks filler content and does not provide a fluoride source.
U.S. Pub. No. 2007/0155853 A1 by Chen et al., is another one-component self-etching self-priming dental adhesive composition. The formulation contains BisGMA (2,2-bis[4-(2-hydroxy-3-methacryloylpropoxy)-phenyl]-propane), DPPA (dipentaerythrytol pentaacrylate), GDM (glycerol dimethacrylate), GPDM (glycerol phosphate dimethacrylate), and PMGDM (pyromellitic glycerol dimethacrylate). The formulation contains both water and an organic solvent such as acetone or ethanol. Additional clinical steps and resin materials are required to bond composite resins to dentin or enamel.
U.S. Pub. No. 2006/0069181 by Thalaker et al. presents a liquid self-etch adhesive that is composed of a carboxylic acid functional polymer and water. This dental adhesive composition consists of two liquid components and contains no fluoride releasing agents or glass fillers. Additional clinical steps and resin materials are required to bond composite resins to dentin or enamel.
U.S. Pub. No. 2007/0248927 A1 by Luchterhandt et al. is a self-adhesive composition based on polyacrylate, Kayamer, MH-P (Methacryloxyhexyl phosphate), MO-P (8-Methacryloxyoctyl phosphate), and MD-P (10-Methacryloxydecyl phosphate) polymerizable compounds. This formula is only photo-curable and requires additional priming step and curing equipment.
U.S. Pub. No. 2007/0203257 A1 by Xuejun Qian, describes a two-part paste/paste self-etch adhering dental composition based on UDMA (reaction product of 2-hydroxyethyl methacrylate with 2,4,4-trimethylhexane diisocyanate), BisGMA, GDM-P (glyceryldimethacrylate phosphate), and GDM (glyceryidimethacrylate). It also contains a solvent, which may increase the oxidation rate of the formula. The formula does not contain any fluoride releasing agent.
U.S. Pub. No. 2005/0277706 A1 by Han et al., describes a highly functional dental adhesive that is based on multifunctional pre-polymer mixture of BisGMA, Tri-GMA, 4-MBTA (4-methacryloxybutyltrimellitic anhydride), MDP, HPMA and water. This adhesive is only photo-curable, which requires additional curing equipment. In addition, this formula contains a maximum of five percent filer material and does not include a fluoride releasing agent.